Archaeological silver objects

Lisa A. Young asked for advice on cleaning the indurate silver
sulfide crust from archaeological objects buried in a reducing
environment.  I find it interesting that this question was asked
given that there is a long history of excavations in the privies of
Alexandria and archaeological conservation that has taken place
there.  My suggestions for Lisa are:

    1.  Can you refer to previous treatment schemes used for this
        material (assuming that the problem has been encountered
        previously, possibly by other excavators and worked on in
        other labs)?  If so, then that might give you protocols to
        follow.

    2.  Is X-ray examination being done on a routine basis for these
        objects in order to determine the shape and extent of any
        remaining uncorroded metal cores?  I think that should be
        done in order to determine the proper course of treatment.

    3.  Have you considered galvanic or electrolytic reduction as at
        least a preliminary cleaning method for the silver and
        silver/composite objects?  The methods and materials are
        discussed in detail in the literature (Hamilton;
        Plenderleith and Werner; Pearson) and I think that those
        methods might be called for here.  Silver sulfide doesn't
        dissolve in hydrochloric acid, and if you are dealing with
        organic composites, you should avoid acids.

Feel free to contact me directly for further discussion.

Paul S. Storch
Objects Conservator
John and Martha Daniels Objects Conservation Laboratory (JMD-OCL)
B-109.1, Minnesota History Center
345 Kellogg Blvd West
St. Paul, MN  55102-1906
651-297-5774
Fax: 651-297-2967

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                  Conservation DistList Instance 12:21
                 Distributed: Thursday, August 27, 1998
                       Message Id: cdl-12-21-001
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